Water is the most important limiting factor of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) cropping systems in semi-arid conditions of Southern Punjab. A two-year field experiment (comprising of cotton-wheat cropping) was conducted in Vehari (Southern Punjab) to calibrate and validate a DSSAT model in the climatic conditions of 1 × CO₂ concentration (conc.) (current). The model simulation during calibration was good with errors up to 4.7, 4.4, 10.1, 6.4 and −5.4% for days to anthesis, days to maturity, total dry matter, yield and HI, respectively for the cotton-wheat cropping system. During model validation, the error percentages were also under reasonable limits. So, the model was run under 2 × CO₂ conc. (future) conditions and it showed a difference of −7.3 to 19.7% anthesis days, maturity days, total dry matter, grain yield, crop ET and WUE_GY with respect to current CO₂ concentration. Simulation by DSSAT showed that the cotton cultivar MNH-886 and wheat cultivar Lassani-2008 were better utilizers of limited water resources under changed climatic conditions in semi-arid conditions of Vehari, which was due to their better water use efficiency. Wheat and cotton cultivars with high water use efficiency would enable crop growth to maintain high crop yields under increased CO₂ and its associated consequences in future.

在旁遮普邦南部半干旱条件下，水分是棉花（Gossypium hirsutum L.）和小麦（Triticum aestivum L.）种植系统的最重要限制因素。在Vehari（旁遮普省南部）进行了为期两年的田间试验（包括棉花-小麦种植），以在1×CO ₂浓度（浓）（当前）的气候条件下校准和验证DSSAT模型。校准过程中的模型模拟效果良好，棉花/小麦种植系统的花期天数，成熟天数，总干物质，产量和HI的误差分别高达4.7％，4.4％，10.1％，6.4％和-5.4％。在模型验证期间，误差百分比也处于合理范围内。因此，模型在2×CO ₂下运行浓 （未来）条件，相对于当前的CO ₂浓度，花期，成熟日，总干物质，谷粒产量，作物ET和WUE _GY的差异为-7.3至19.7％。DSSAT模拟结果表明，棉花品种MNH-886和小麦品种Lassani-2008在Vehari半干旱条件下，在气候条件变化的条件下，是有限水资源的较好利用者，这是由于它们具有更好的水分利用效率。高水分利用效率的小麦和棉花品种将使作物生长在CO ₂增加及其相关后果的影响下保持高作物产量。